This invention relates to monitoring component holders on a component placement machine.
Component placement is one of the most labor and data intensive operations in electronic board assembly. Current high-speed component placement equipment can place up to 10,000 to 30,000 components per hour, depending on configuration, and can carry up to 1,000,000 or more individual components.
Surface mount components are typically supplied by component vendors as rolled tapes of components that must be loaded onto individual feeders, sometimes called component dispensing cartridges, that can then be mounted in corresponding feeder slots on the machine. These rolls of components (up to, in some cases, 10,000 or more components per roll) may be loaded onto the feeders either at a stock room or at the machine, and the loaded feeders then loaded into feeder slots. Some components are supplied in tubes or in trays rather than on rolled tape, and must also be placed in a specified location on the machine for picking. As used herein, the term xe2x80x9ccomponent holderxe2x80x9d is intended to encompass rolled component tape feeders, component tube holders, component bins, and other types of devices for holding a quantity of components for picking. The term xe2x80x9ccomponent holder receptaclexe2x80x9d means a space on a placement machine for receiving any one of a number of holders, such as a feeder slot.
Component placement machines can have many component holder receptacles (e.g., 150 or more), each accessible by a placement turret or other picking mechanism that picks individual components from the holders in the receptacles and places them in particular locations on a printed circuit board, according to programmed instructions. For application flexibility, each holder and receptacle is generally constructed to be compatible with many different components.
Two classes of placement machines are currently available in the surface mounted component placement equipment market. The turret type of placement machine has a rotating turret on which 10-20 placement heads are mounted. The turret rotates about a fixed vertical axis. The printed circuit board is mounted on a moving table on one side of the turret, and there is a moving bank of feeders on the opposite side of the turret. The turret picks components from the feeders on one side, while placing previously picked components on the other side of the turret. In the gantry type of machine, the printed circuit board and the feeders remain stationary during the placement process, and a pick mechanism is moved on an overhead gantry system. The pick mechanism moves between different feeders to pick up components and then place them onto the printed circuit board. Multi-head gantry systems employ ten to twenty gantry pick mechanisms xe2x80x98gangedxe2x80x99 together to increase the throughput of the machine.
Some prior art attempts to catch assembly errors on gantry-type machines featured manual scanning by the operator. Scannable bar code labels are placed near each slot on the machine. After selecting the machine placement program and loading the program into the system, and just before putting a feeder onto the placement machine, the operator would scan the component part number from the reel in the feeder and then scan the slot number on the placement machine where the feeder was to be located. The system would compare the part number and slot number with the part numbers and slot numbers in the program, and alert the operator if the scanned information did not match the program. If no error was detected, the operator would be prompted to place the feeder onto the placement machine in the scanned slot. Hopefully, the operator would place the feeder in the same slot as scanned.
To improve on the system with manual scanning of part number and slot number, some systems eliminate scanning of the slot number by incorporating a sensor on the slot to sense the presence and absence of a feeder. Just before putting a feeder onto the placement machine, the operator scans the component part number from the reel in the feeder. Then, within a predetermined period of time (e.g., 20 seconds), the operator must place the feeder onto the placement machine. The sensor triggered by the feeder identifies the slot number on which the feeder is placed. If the slot number and part number pair does not match the slot number and part number pair in the placement program, an alarm sounds. All verification is done right next to the machine, with production stopped while the feeders are individually loaded and verified during setup.
In what is sometimes referred to as the xe2x80x9csmart feederxe2x80x9d approach, each feeder is embedded with an erasable, programmable read-only memory (EPROM). As the operator loads a component reel into a feeder, he loads the component""s part number (hopefully, matching the part number of the components just loaded onto the feeder) into the feeder""s EPROM. The placement machine is built with EPROM readers integrated into each slot. When the feeder is placed into a slot, the machine reads the part number in the EPROM. Since the placement machine knows the slot number location of each part number, the placement program is no longer driven by slot number but is driven by part number. For example, part number xe2x80x9c12345xe2x80x9d can be placed in any slot on the placement machine and the placement machine will go to the correct slot to pick a component with part number xe2x80x9c12345xe2x80x9d. If a different component is to be loaded onto the feeder, the feeder EPROM must be reprogrammed.
The physical arrangement of components, feeders and slots must be in accordance with the expected arrangement as programmed in the machine. Any error in the arrangement can cause a corresponding error in the placement of components on the board. In a high volume, low mix manufacturing environment, a component loading error can produce a high number of defective printed circuit boards in a short period of time. In a low volume, high mix environment the chance of component loading error increases because of frequent feeder manipulation for product change over. If a wrong component is loaded onto the feeder, or the feeder is placed into a wrong slot on the machine, an assembly error is introduced. Because a placement machine can assemble thousands of printed circuit boards in a short time period, an assembly error due to wrong component placement can quickly cause major losses of time and money.
The invention features a system for guarding against some of the typical loading errors that can occur even with the most conscientious machine operators, as well as providing much-needed inventory and maintenance data.
According to one aspect of the invention, an improvement is provided in a machine for placing electronic components on a printed circuit board. The machine has a series of electronic component holder receptacles for storing electronic components, and a movable pick head for picking selected components in a programmed sequence from component holders placed in the holder receptacles, and placing the picked components in designated locations on a circuit board. In my improvement, the component holder receptacles each have an associated, adjacent key receptacle for receiving a machine-readable holder identification key attached to a component holder to be loaded into the key receptacle after the component holder is loaded into the holder receptacle. The machine also has a controller constructed to identify, from identification keys inserted into the identification key receptacles, the loaded component holders to which the keys are attached.
In some embodiments, the identification keys each include a programmable memory containing holder-specific data, such as remaining component inventory.
In a preferred embodiment, the key receptacles of the component holder receptacles are connected serially, for communicating with the controller over a common data path. The key receptacles of the component holder receptacles each sequentially increment and relay downstream a communication received from the controller, and transfer data to the controller indicating their position along the data path.
The component holder receptacles may be arranged in a first interchangeable bank with their associated key receptacles forming a first key receptacle string, with others of the component holder receptacles arranged in a second interchangeable bank with their associated key receptacles forming a second key receptacle string. The key receptacle strings each have an input serial connector and an output serial connector, for connecting the strings serially for communication with the controller when the interchangeable banks of component holder receptacles are docked on the machine.
In some cases, the controller is constructed to communicate serially with the data keys while the movable pick head is picking electronic components from their associated component holders.
The machine also has, in some configurations, a circuit board output sensor for detecting an assembled board being unloaded from the machine. The controller is constructed to decrement stored inventory values associated with the loaded component holders by programmed amounts, in response to a signal received from the circuit board output sensor. The controller may also, for example, sound an alarm in response to a negative component holder inventory value.
Similarly, the machine may have a circuit board input sensor for detecting a board being loaded onto the machine for component assembly, with the controller constructed to initiate a component holder placement verification sequence in response to a signal received from the circuit board input sensor. In such cases, the component holder placement verification sequence may include polling the data key receptacles for information regarding their location and identification of any component holder loaded in their associated component holder receptacles.
According to another aspect of the invention, a component holder (for holding a quantity of electronic components on an electronic component placement machine) has a machine-readable holder identification key attached to the holder by a flexible cable and containing holder identification information, for insertion into an associated machine data key receptacle when the holder is loaded onto the placement machine.
The identification key, in some embodiments, contains a programmable memory containing holder status information, such as including a part number associated with an electronic component loaded onto the holder, a loaded component quantity, holder maintenance data, or an indication of whether the holder has undergone a specific process, such as a heating cycle, for examples.
According to another aspect of the invention, an improved method of tracking electronic placement machine component holder status is provided. The method includes:
(1) assigning a specific, machine-readable identification code to each one of a set of component holders;
(2) updating a stored relationship between holder identification code and component part number when installing a different set of components on the holder; and
(3) electronically reading the identification codes of component holders installed on a placement machine to identify the installed component holders and their individual positions on the placement machine.
According to another aspect of the invention, a package of electronic components includes a housing adapted to be inserted into a component feeder of a placement machine, a multiplicity of electronic components contained within the housing and arranged to be sequentially picked from the package by the placement machine, and a removable label affixed to the package. The removable label has an adhesive backing for remounting the label, after removal from the package, on a component feeder, and light-scannable information printed thereon for identifying the components of the package. Preferably, the package has a multiplicity of such removable labels, for multiple remountings of the package on different feeders.
Features of some embodiments of the invention are disclosed in my U.S. Pat. No. 6,027,019, the entire contents of which are hereby incorporated by reference as if entirely set forth.
The apparatus is particularly well suited for use in placement machines for mounting electronic components on circuit boards. Such machines generally have a series of feeder slots for holding component feeders, and a picking device constructed to pick components from the feeder slots for mounting to a circuit board.
The invention can reduce the chance of component loading error by checking the arrangement of component feeders on a placement machine during a multi-board build and alerting the operator before a mistaken component is placed. Advantageously, the system does not require the machine to sit idle while component arrangement is checked, and the re-verification process can occur during the loading of each board. In addition, the invention can provide accurate component inventory information and track individual feeder use for maintenance purposes, and can detect some feeder replenishment errors through part counting. The components of the system are readily installed on conventional placement machines as an aftermarket addition, and do not interfere with the basic picking operation of the placement machine.
The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.